The present invention relates to a method for cleaning squeeze rollers in an apparatus for liquid electrophotographic development and a liquid electrophotographic developing method suitable for running process.
A schematic sectional view of a conventional electrophotographic developing apparatus is shown in FIG. 5. Corona charged and imagewise exposed electrophotographic photoreceptor 1 is led into a pair of development electrodes 9 and 10 by a pair of feed rollers 4 and 5 in the direction of the arrow in FIG. 5. Liquid developer 2 is uniformly fed from developer supplying slit 11 to development electrodes 9 and 10 by a pump (not shown) and is filled therein.
The electrophotographic photoreceptor developed in development electrodes 9 and 10 is passed through squeeze rollers 6 and 7 to remove excess liquid developer and then is delivered to the subsequent steps (e.g., drying and fixing steps). Cleaning pad 8 is made of a resilient material such as, for example, cotton in order to effectively remove fog and is held against upper squeeze roller 6 so that it wipes the roller by revolution of the roller and the excess developer removed from the surface of photosensitive layer of the photoreceptor is prevented from being again applied to the surface of the photosensitive layer from the roller.
The cleaning method using a cleaning pad is disclosed, for example, in Japanese Patent Kokai (Laid-Open) Nos. 50-15561, 50-98844 and 51-118437 and Japanese Utility Model Kokai (Laid-Open) No. 56-126656. However, such methods still do not have sufficient cleaning effect. Especially, a developing apparatus is not so often used in succession and is stopped during the night or on a holiday. During this stopping period the developer containing toners and remaining on the squeeze rollers is evaporated and sticks to the rollers as a film upon drying and besides the concentrated toners are locally hardened and damage the surface of the upper squeeze roller 6 when operation is restarted. Sometimes the squeeze rollers per se or cleaning pad 8 and the upper roller stick to each other to hinder the driving of the apparatus.
In case such intermittent developing treatment is carried out for a long time in running procedure, there are the problems such as consumption of liquid developer by electrophotographic photoreceptor and change in amount and composition of the liquid developer caused by evaporation of solvent in addition to the problem of sticking of squeeze rollers.